Electrosurgical instruments are well known and widely used in the medical, dental, and veterinarian fields. They offer the capability of precision cutting with electrosurgical currents using a handpiece with needle, ball, or loop electrodes in a monopolar operating mode, or convenient coagulation using a forceps in a bipolar operating mode. Ellman International, Inc., of Oceanside, N.Y. makes available an electrosurgical instrument which provides on its front panel connectors for receiving the plug of a unipolar handpiece and a ground or indifferent plate, as well as a connector for receiving the plug of a bipolar forceps cable.
In a typical surgical setting, a surgeon may first use the unipolar handpiece to perform a desired cutting procedure and then desire to use the bipolar forceps for coagulation of blood vessels because of its unique ability to coagulate in a fluid field. One possible solution which maintains the requisite sterile field while still allowing the surgeon to unplug and plug in different devices from or to the instrument is described in U.S. Pat. No. 5,954,686, whose full contents are herein incorporated by reference. In the solution proposed in this patent, the electrosurgical instrument is configured to generate two MHz carrier frequencies, the higher one of about 4 MHz for operation in the CUT, and CUT/COAG modes, and the lower one of about 2 MHz for operation in the HEMO and FULGURATE modes. These four operating modes typically are represented by CUT: full-wave rectified and filtered CW output with maximum average power; CUT/COAG: full-wave rectified but unfiltered, deeply modulated (at 37.5 or 75 Hz rate) envelope output with approximately 70% average to peak power ratio; HEMO: half-wave rectified and unfiltered, deeply modulated (at 37.5 or 75 Hz rate) envelope output with approximately 35% average to peak power ratio; FULGURATE (or Spark-Gap Wave): deeply modulated (3.6 KPPS random rate) with approximately 20% average to peak power ratio. Selection of the bipolar mode will normally select the HEMO mode.